It is known in the art relating to digital and film single reflex lens cameras having a viewfinder to utilize mounting rails or a similar attachment means on an outer portion of the viewfinder frame to mount various accessories to the camera viewfinder. Conventional accessory mounting devices include multiple parts that engage the mounting rails from the right or left hand side below the rails to lock the mounting device into place over the viewfinder. Alternatively, conventional accessory mounting devices lock into place over the viewfinder by locating and slipping into detents disposed midway in the rail channel. Also, some conventional accessory mounting devices do not lock into place. These conventional accessory mounting devices all have the problem that they tend to insecurely mount to a camera and often fall off the camera.